The present invention relates to a filter device as generically defined by the preamble to claim 1.
Textile machines, especially those operating by the so-called open-end spinning process, have many pneumatically operated devices and systems and therefore as a rule have a negative pressure system as a part of the machine itself that furnishes the negative pressure required for the spinning process at the open-end spinning units.
Such negative pressure systems essentially comprise a negative pressure source, such as a suction fan, a filter device upstream thereof, and a suction conduit extending the length of the machine, to which the individual open-end spinning units are connected via branch lines.
In many of the known open-end rotary spinning machines, a transverse suction duct is often also connected to the filter device, for pneumatically supplying a service unit, e.g., a vacuuming device for cleaning the dirt conveyor belts of a mechanical dirt disposal device located below the spinning units.
The filter device has at least one filter chamber. Located inside the filter chamber, usually crosswise to the flow of suction, is a filter element, for filtering the aspirated air which typically is contaminated with dirt particles and fibers. Thus, the filter element traps the dirt particles and fibers in the filter chamber.
However, a disadvantage of these known devices is that the filter element becomes clogged by the aspirated particles after only a relatively short time, which leads to a marked pressure drop in the negative pressure system of the textile machine. In turn, since open-end spinning machines always require a minimum negative pressure for the production process, the filter elements in the known devices must be cleaned at relatively short intervals.
For this reason, it has already been proposed to equip filter devices with two filter chambers that can be acted upon separately. In these filter devices, known for instance from German Patent Disclosure DE 30 10 011 A1, one of the filter chambers at a time is acted upon by negative pressure, while at the same time the filter element of the other filter chamber can be cleaned. In this known device, a plurality of incoming air flaps, shutoff flaps, and diversion flaps are provided for deflecting the air flows inside the filter device, and are coupled together via a lever linkage and triggered by means of a pneumatic cylinder. Because of its quite complicated flap control among other things, this known device requires a relatively large amount of space.
A comparable filter device that is somewhat more compact and is markedly simpler in design in its arrangement of the diversion flaps is known from German Patent Disclosure DE 26 44 274 A1. A disadvantage of this device, however, is the relatively short intervals required between cleanings.
To lengthen the cleaning intervals, it has also been proposed (e.g., German Patent Disclosure DE 39 00 543 A1) that a fine-pore filter medium be employed, which is multiple times larger than the active filter surface area. The filter medium is arranged in the filter chamber in a manner enabling it to be shifted from a readiness position to an active filter position and therefrom, after being exhausted by becoming soiled, can be shifted to a disposal position. The replacement of the filter medium can be done automatically by means of a feeding system as a function of the degree of soiling, which is ascertained by a soiling sensor. However, even this known device has not been established in practice.
For lengthening the cleaning intervals, it is also known to dispose a filter element in a filter chamber in a manner such that the filter element is at least partially self- cleaning. One such filter chamber is described for instance in German Patent Disclosure DE 198 36 065.7, published after the filing date of the present application. The negative pressure system of the textile machine has a filter chamber with two screen elements disposed in an L-shape. One of the screen elements is operative as a relief screen and is spaced apart in the filter chamber from the side wall of the filter chamber in such a way that a flow of suction occurring between the suction conduit connection and the connection for the negative pressure source extends virtually parallel to this relief screen. A second screen element, spaced apart from the filter chamber bottom, is operative as a collector screen and is positioned approximately orthogonally to the flow of suction.
This disposition of the filter screens inside the filter chamber assures that the predominantly very fine dirt and fiber particles that reach the filter chamber via the suction conduit connection are deposited immediately and remain on the collecting screen. The relief screen, over which the flow of suction initially sweeps virtually parallel, remains maximally free of dirt particles for an extended time. Thus, this previously described filter device can achieve cleaning intervals of a length previously unknown.
In view of the above-described prior art, it is an object of the present invention to provide a filter device which, on the one hand, has extended cleaning intervals and, on the other hand, can be cleaned as needed without impairing regular ongoing spinning operation or causing other problems.
This object is attained according to the present invention by a filter device for a suction system of a cheese-producing textile machine which basically comprises at least one filter chamber, an intermediate chamber connected to the filter chamber, and a negative pressure source connected to the intermediate chamber. Preferably, the filter device has two filter chambers with the intermediate chamber therebetween and at least one of the filter chambers is sub-divided into a main filter sub-chamber and a reserve filter sub-chamber. According to the present invention, a closure mechanism is associated with the intermediate chamber for selectively communicating the negative pressure source with the filter chambers. The closure mechanism includes suction openings for communicating the intermediate chamber with the main filter sub-chamber and the reserve filter sub-chamber and closure elements respectively associated with the suction openings and functionally coupled with one another for closing and opening the suction openings alternately. In this manner, the intermediate chamber communicates alternately with the main filter sub-chamber and the reserve filter sub-chamber.
The present invention thusly combines the advantages of the filter devices known from the prior art, yet without having their disadvantages. That is, the filter device of the invention is distinguished not only by a compact structure and long cleaning intervals but also, as needed, by good accessibility of the filter elements to be cleaned. In addition, during the cleaning of the filter elements, both regular spinning operation and the supply of negative pressure to the surface unit remain maximally unaffected. Maintaining the negative pressure level even while the filter is being cleaned has a favorable effect on the utility of the service unit in the region of the transverse suction duct and thus in the final analysis on the total efficiency of the open-end spinning machine as well.
A preferred embodiment of the invention provides the advantageous feature of mechanically coupling the closure elements for the suction openings of the main filter chambers with the closure elements for the suction openings of the reserve filter chambers. This kind of mechanical coupling arrangement enables not only a defined opening and closing of these suction openings but also furnishes a very sturdy and thus long-lived device, which can moreover be produced economically.
Since the main filter chambers, before their cleaning doors are opened, must be maximally free of negative pressure, it is also provided, that one pressure equalization opening is disposed in the region of each of the main filter chambers. The pressure equalization opening is automatically opened upon closure of the suction openings of the main filter chambers. In this manner, it is assured that the negative pressure in the main filter chamber drops far enough that the cleaning door can be removed without problems. Preferably, the cleaning door is mounted to be openable from outside the filter device which facilitates manual cleaning if desired.
The preferred embodiment also has a closure disposed between the main filter chamber and the reserve filter chamber and the cleaning door includes a mechanism connected with the closure for closing the closure when the cleaning door is opened. More specifically, a lever disposed on the closing mechanism engages a pivotably disposed flap from behind and lifts it onto a frame disposed between the filter chambers. Under the influence of the negative pressure prevailing in the reserve filter chamber, the flap remains on this frame even after the cleaning door has been removed and thus partitions off the main filter chamber from the reserve filter chamber.
In the preferred embodiment, the filter device has two substantially identical filter chambers, which are preferably disposed symmetrically with respect to the longitudinal center axis of the machine and in mirror-image to one another.
One of the filter chambers communicates with a suction conduit which extends the length of the machine and to which the numerous open-end spinning devices are connected. The generous dimensioning of the suction conduit assures that an adequate and approximately constant negative pressure will always be applied to all the open-end spinning devices, which is indispensable if optimal spinning is to be obtained.
The other filter chamber communicates with vacuuming devices for the dirt conveyor belts and with transverse suction ducts by which negative pressure required by the service units is furnished. By separating the individual flows of suction, a drop in negative pressure, as can happen in operation of the service unit, is prevented from adversely affecting the negative spinning pressure required at the open-end spinning devices.
Further features, details and advantages of the present invention will be recognized and understood from an exemplary embodiment described below in conjunction with the accompanying drawings.